1. Field of the Invention
The present inventions relates to a drawing registration method of registering a drawing contained in a map or a drawing described by a photo-electro transfer device such as a scanner or TV camera in a data base and more particularly to a drawing recognition method valid in recognizing and registering a drawing indicated by a group of a plurality of similar lines such as contour lines.
2. Description of the Prior Art
As a conventional drawing recognition method, many preceding researches on automatic input of information of contour lines have been reported. For example, in Reference 1: Agui and 2 others, "Research on mountainous geographical map information" (Electric Communication Society Report, PRL81-37, 1981), a method of performing the thinning process for a mountainous geographical map image to be inputted, extracting a contour line candidate from decision of whether it is a long vector component or not, and connecting the contour line candidate interrupted by characters and symbols mutually on the basis of the vector angle is proposed. However, this method causes a problem that since the decision of vector angle is local, many connection errors occur.
On the other hand, in Reference 2: Mizutani and 3 others, "Extraction of contour lines using the adjacent relation by a Voronoi-line graph" (Technical Report of the Institute of Electronics, Information and Communication Engineers, D-II, Vol. 1, J74-D-II, No. 11, 1991), a method of preparing a Voronoi-line graph so as to grasp the global adjacent relation of line segments, obtaining an adjacent graph between these line segments, and connecting the interrupted contour component lines correctly is proposed. This method reduces connection errors from decision of the adjacent graph. However, in a portion where contour lines are crowded in a narrow area and jointed as a drawing or a portion where lines are interrupted by numeric characters indicating elevation and cliff symbols, it is impossible to recognize contour lines perfectly and many recognition errors occur. Therefore, when automatic recognition using the aforementioned batch processing input method is performed, a concentrated error check is often requested to an operator. This concentrated error check requires enormous labor, so that a problem arises that the entire cost from input to output for the system will not reduce.
Therefore, as shown in Reference 3: Yamakawa and 1 other, "Interactive drawing input system" (Nikkei Computer Graphics, April issue, 1987, pp. 120 to 130), a man-machine based automatic recognition method in which decision of an operator is reflected positively from the initial stage of vectorization is widely noticed. In this man-machine based automatic recognition method, when the vectorization direction is not automatically decided, the vectorization direction is decided by an inquiry to an operator from the system, so that an unnecessary operation required for error check can be cut down. However, since the system is structured so that whenever a portion where the tracing direction is not automatically decided such as a junction part or an interruption part of contour lines appears, the tracing direction, that is, the vectorization direction is inquired, the burden imposed on an operator (user) is severe.
On the other hand, separately from this flow, many researches on recognition of the whole by describing a drawing to be traced structurally according to the relation between the whole and the parts and confirming the consistency between parts traced successively have been reported. For example, in Reference 4: Nakamura and 1 other, "Extraction of image characteristics by parallel trace" (Artificial Intelligence Society Journal, Vol. 8, No. 1, pp. 65 to 78, 1993), it is proposed to realize characteristic extraction on the basis of this structure description by a cooperative action of a multi-agent. This method enables to decide a process dynamically at execution time without detailed description on the processing flow and highly precise image recognition by self-adjusting problem solving is expected. However, in this method, there is a possibility that an enormous calculation time is required due to an explosive increase of combinations. Furthermore, in a drawing having a complicated shape such as contour lines, structure description itself is not clear. Therefore, the present invention proposes a method of constituting a system with a recognition agent for recognizing a path in correspondence to a plurality of adjacent lines designated by an operator one by one and a supervisor agent for supervising the whole as application of the multi-agent theory to drawing recognition. This method enables highly precise recognition by describing an autonomous action of each agent and a cooperative action between the agents. However, when two agents are set in correspondence to one contour line due to incorrect assignment of agents, a problem arises that an incorrect recognition result is obtained because the cooperative action between the agents is not performed correctly. To realize highly precise recognition by a cooperative action of a multi-agent, an art for automatically changing assignment of agents so as to set agents correctly is important.
As an example in which changing of agent assignment is realized, Reference 5: Gyoten and 3 others, "Multi-agent system for separation of characters from a document image" (Technical Report of the Institute of Electronics, Information and Communication Engineers, AI95-37, PRU 95-152, pp. 21-26) may be cited. In this reference, the spatial distributed method in the multi-agent theory is applied to a problem of separation of characters in a document image and one agent is set in correspondence to one character string in the document image. However, character separation and drawing recognition are different in the recognition object, so that the agent assignment used for character recognition and the assignment error detection method cannot be used for the drawing as they are.
Description of an autonomous action of each agent and a cooperative action between the agents enables highly precise recognition. However, when two agents are set in correspondence to one contour line due to incorrect assignment of agents or agents are set in correspondence to a component other than contour lines, a problem arises that an incorrect recognition result is obtained because the cooperative action between the agents is not performed correctly.